Method for evaluating percussion performance of closing-in rope cutter

Abstract

The invention provides a closing-in rope cutter firing performance evaluation method, which comprises the steps of obtaining a reliable firing pull-off angle range through a closing-in rope cutter ground firing test, and fitting a relation curve of a pull-off angle and a pull-off force; establishing a dynamic simulation model, wherein the dynamic simulation model comprises a closing rope cutter model, an aircraft model and a connecting rope between the closing rope cutter and the aircraft; setting initial conditions of multi-working-condition simulation, carrying out dynamic simulation, and obtaining pull-off angles of all working conditions; judging whether the pull-off angles of all the working conditions are within a reliably-fired pull-off angle range or not, and if the pull-off angles of all the working conditions are within the reliably-fired pull-off angle range, determining that the firing performance of the closing-in rope cutter is reliable; otherwise, the percussion performance of the closing rope cutter does not meet the use requirement. The problems that the ground test cannot simulate the drawing percussion under the condition of free rotation of the closing rope cutter, and the percussion performance under the flight condition cannot be determined are solved.

Description

Technical Field

[0001] This invention belongs to the field of aerospace aerodynamic deceleration technology, and specifically relates to a method for evaluating the firing performance of a cord cutter. Background Technology

[0002] In the aerospace field, parachutes are important aerodynamic deceleration devices, typically made of soft, special-textured materials. The zipper cutter is a crucial component in the operation of parachutes and other textile products, performing designated functions (such as staged parachute opening to reduce opening load, or timed release of anchors) by delaying the cutting of ropes or straps. It is widely used in the recovery of parachutes from satellites and spacecraft.

[0003] A cord cutter typically consists of a cutting assembly, a delay assembly, and a firing assembly. The structure of the firing assembly is shown below. Figure 2 , Figure 2 Number 1 is the firing lug, number 2 is the firing pin, number 3 is the spring, and number 4 is the delay tube cap. The firing assembly is the firing mechanism of the cord cutter. When using a cord cutter, a cord is usually connected to the firing lug to provide pulling force. When the cord is taut and under force, it pulls off the firing lug. After the firing pin is unrestrained, it pierces the delay tube cap under the action of the spring force, thus activating the delay assembly.

[0004] To ensure the proper functioning of the cord cutter, the pull-out force design of the firing assembly must meet design requirements and undergo thorough testing and verification. This ensures both product safety during storage and transportation and reliable firing during operation.

[0005] The commonly used method for evaluating the firing performance of cord cutters is the ground firing test. This typically involves fixing the cord cutter in a given position, applying a pull force at a given angle to the firing lug until it is pulled out, recording the pull-out force (the pull force when the firing lug is pulled out), and observing the firing process. However, during ground tests of cord cutter firing assemblies, it was found that for the same cord cutter, the pull-out force varied depending on the angle at which the firing lug was pulled out, and at some angles that deviated from the design expectation (usually the pull-out angle was smaller than the design expectation, defined as...), the pull-out force was inconsistent. Figure 2 When α (where α is the angle between the pull-out force F and the axial direction of the cutter) is pulled out, structural damage may occur, causing the firing pin to jam and fail to fire.

[0006] Unlike ground-based firing tests, in actual parachute flight operations, the attitude of the drawstring cutter is not fixed in the air. When the rope connecting to the firing lug provides pull force, the drawstring cutter moves accordingly, causing the angle of pull force to change along with the rope elongation. Ground tests can only assess the reliable firing angle and pull force of the drawstring cutter, but cannot analyze whether the actual pull angle during dynamic processes matches the design expectations, making it difficult to evaluate firing performance under flight conditions. Validation through flight tests can only verify the state of a very limited number of flight conditions, and the development and testing cycle for comprehensive testing is too long. Furthermore, if the drawstring cutter fails to fire during flight tests, it often leads to the risk of subsequent parachute failure, resulting in significant safety issues and economic costs.

[0007] This invention addresses the problem of evaluating the firing performance of a cord cutter during the aforementioned process by proposing a method for evaluating the firing performance of a cord cutter. Based on ground firing test data and combined with dynamic analysis methods, the method analyzes the motion and pull-out states of the cord cutter under tension in a free state, making the evaluation of the firing performance of the cord cutter more accurate. Summary of the Invention

[0008] In order to overcome the shortcomings of the existing technology, the inventors have conducted intensive research and provided a method for evaluating the firing performance of a cord cutter. This method solves the problem that ground tests can only evaluate the pull-out angle and pull-out force of a cord cutter through static tests, but cannot analyze the actual pull-out angle during dynamic processes, and therefore cannot accurately evaluate the firing performance of the cord cutter.

[0009] The technical solution provided by this invention is as follows:

[0010] Firstly, a method for evaluating the firing performance of a cord cutter includes:

[0011] By conducting ground firing tests on the cord cutter, the range of pull-out angles for reliable firing of the cord cutter was obtained, and the relationship curve between the pull-out angle and the pull-out force was fitted.

[0012] A dynamic simulation model was established, including a model of the drawstring cutter, an aircraft model, and a connecting rope between the drawstring cutter and the aircraft. The connecting rope was simplified to the spring force of the simulated pull-out force applied between the firing lug of the drawstring cutter and the aircraft.

[0013] Set the initial conditions for multi-condition simulation, carry out dynamic simulation, and obtain the pull-out angle for all conditions using the relationship curve between pull-out angle and pull-out force.

[0014] Determine whether the pull-out angle for all working conditions falls within the reliable firing range of the cord cutter. If the pull-out angle for all working conditions falls within the reliable firing range of the cord cutter, then the firing performance of the cord cutter is reliable. If the pull-out angle for any working condition exceeds the reliable firing range, then the firing performance of the cord cutter does not meet the usage requirements.

[0015] Secondly, a device for evaluating the firing performance of a cord cutter includes:

[0016] One or more processors;

[0017] Storage device for storing one or more programs.

[0018] When the one or more programs are executed by the one or more processors, the one or more processors implement the firing performance evaluation method for the cord cutter described in the first aspect.

[0019] Thirdly, a readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method for evaluating the firing performance of a cord cutter as described in the first aspect.

[0020] Fourthly, a computer program product comprising: a computer program (also referred to as code or instructions) that, when run, executes the method for evaluating the firing performance of a cord cutter as described in the first aspect.

[0021] The method for evaluating the firing performance of a cord cutter provided by the present invention has the following beneficial effects:

[0022] This invention provides a method for evaluating the firing performance of a cord cutter. Based on ground firing tests, it combines dynamic analysis methods to analyze the firing performance of a cord cutter in free state under given flight conditions. This solves the problem that ground tests cannot simulate pull-out firing under free rotation of the cord cutter, and cannot clearly define the firing performance under flight conditions. At the same time, the use of dynamic simulation is convenient and efficient, which can greatly promote the development progress and improve the firing reliability of the cord cutter.

[0023] This invention is used to evaluate the firing performance of a cord cutter, and can also be extended to other pyrotechnics and control structures that are triggered by mechanical pulling, as well as their pull reliability. Attached Figure Description

[0024] Figure 1 This is a flowchart of the firing performance evaluation method for the cord cutter of the present invention;

[0025] Figure 2 A schematic diagram of a cord cutter;

[0026] Figure 3 Schematic diagram for setting the initial pull-out angle α of the cord cutter;

[0027] Figure 4 This is a schematic diagram of the dynamic analysis model;

[0028] Figure 5 The figure shows the relationship curve between the fitted pull-out angle and the pull-out force in the example.

[0029] Figure 6 This is a diagram showing the relationship between the pulling force and the pulling angle of the cutter under various working conditions during the dynamic process in the embodiment. Detailed Implementation

[0030] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0031] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0032] This invention provides a method for evaluating the firing performance of a cord cutter. Based on ground firing test data, it clarifies the range of pull-out angles for reliable firing of the cord cutter and fits a curve showing the relationship between pull-out force and pull-out angle. Using dynamic analysis, it analyzes the motion and pull-out states of the cord cutter under tension in a free state, obtaining the firing performance of the cord cutter under given initial conditions, thus making the evaluation of the firing performance of the cord cutter more accurate.

[0033] like Figure 1 As shown, the method for evaluating the firing performance of the cord cutter includes the following steps:

[0034] Step 1: Obtain the range of pull-out angles for reliable firing of the rope cutter through ground firing tests, and fit the relationship curve between the pull-out angle and the pull-out force.

[0035] To obtain the possible initial pull-out angle range during actual flight, set up pull-out angle conditions for ground firing tests, ensuring that the pull-out angle range of the ground tests encompasses the possible initial pull-out angle range during flight. Fix the cable cutter at a given angle, and use a pulling tester to pull off the firing lug at the given angle, recording the pull-out angle and the pull-out force at that angle. Determine the reliable firing pull-out angle range of the cable cutter based on the maximum and minimum pull-out angle values. After completing all angle tests, use linear interpolation to fit the relationship curve between the pull-out angle and the pull-out force.

[0036] (1) Obtain the possible initial pull-out angle range during actual flight.

[0037] Based on the installation angle range of the retractor cord cutter in the parachute pack and the angle range of the parachute pack axis deviating from the direction of the pull force (i.e. the direction of the parachute cord straightening) during the parachute pull-out process, the possible initial pull-out angle range during actual flight can be obtained.

[0038] During actual flight, the initial pull angle α of the retractable cord cutter is related to the installation angle θ of the cutter in the parachute pack and the angle β of the parachute pack axis deviating from the direction of the pull force. (See...) Figure 3 The actual relationship is a complex three-dimensional geometry, but it's easy to see from the geometry that when the angle θ at which the cutter is installed in the parachute pack and the angle β at which the parachute pack axis deviates from the direction of the tension are determined, α is minimized when the initial pull angle α of the drawstring cutter is in the same plane as the other two angles. Therefore, it is acceptable. α max Just take π.

[0039] (2) Ground firing test of the cord cutter

[0040] Based on the aforementioned possible initial pull-out angle range α during actual flight... min ~α max Set appropriate experimental angles (α1, α2, ..., α n The working conditions cover the boundary values ​​of the initial pull-out angle range. Using a fixture, the cord cutter is fixed at a given test angle. A tensile testing machine is used to pull out the firing lug at the given angle, and the pull-out force at that angle is recorded. After completing all angle tests, a linear interpolation method is used to fit the relationship curve between the pull-out angle and the pull-out force.

[0041] Step 2: Establish a dynamic simulation model. Based on Adams software or other dynamics software, establish a dynamic analysis model, including a rope cutter model, an aircraft model, and the connecting rope between the rope cutter and the aircraft. The connecting rope is simplified to the spring force of the simulated pull-out force applied between the firing lug of the rope cutter and the aircraft. See [link to relevant documentation]. Figure 4 .

[0042] To set up a model for a cord cutter, you need to set its geometry, center of mass, mass characteristics, and moment of inertia.

[0043] Setting up an aircraft model requires defining its mass characteristics. Furthermore, since the pull force of the cutter is usually small and the moment of inertia of the aircraft is large, the attitude change of the aircraft can be ignored, and the aircraft can be simplified as a point mass model.

[0044] To set the spring force that simulates the pulling force applied between the firing lug and the aircraft, the spring force length and elastic coefficient need to be set to the length and elastic coefficient of the firing lug pull rope and the connected rope, and it should be set to be under tension force, and not under shortening force.

[0045] Step 3: Set the initial conditions for the simulation. Typically, multiple uncertainties are considered, such as the initial pull-out angle α of the retractable cord cutter, the aircraft speed, the pull-out speed during the parachute pull-out process, and the speed of the retractable cord cutter. The conditions are set to cover the boundary values ​​of various angle and speed conditions.

[0046] According to the pull-out angle range α of the cord cutter min ~α max The attitude angle of the retractable rope cutter before it is pulled is set to ensure the initial pull angle α. The positions and velocities of the retractable rope cutter and the aircraft are set according to the actual position and velocity of the retractable rope cutter and the aircraft during flight.

[0047] Step 4: Conduct dynamic simulation to obtain the pull-out angle for all working conditions. During the dynamic analysis, start from the initial unpulled state. Due to the relative motion between the cable cutter and the aircraft, the firing lug pull rope and connected ropes begin to elongate, the pull force gradually increases, and the pull-out angle gradually changes (according to...). Figure 2 (The drawing angle is typically gradually increasing). The calculation terminates when the drawing force is greater than or equal to the pull-out force at the corresponding drawing angle. The drawing angle at this point is the pull-out angle under this working condition, where the pull-out force at the drawing angle is obtained using the relationship curve between the pull-out angle and the pull-out force.

[0048] Step 5: Evaluate the firing performance of the cord cutter. For the pull-out angles obtained in Step 4, if all pull-out angles are within the reliable firing range of the cord cutter, then the firing performance of the cord cutter is reliable. If any pull-out angle exceeds the reliable firing range for a given condition, then the firing performance of the cord cutter is not suitable for that operating condition.

[0049] If it is determined that the firing performance of the cord cutter is not suitable for the operating conditions, the firing reliability can be improved by controlling the initial installation angle of the cord cutter, the pull-out speed during the parachute pull-out process, or improving the performance of the firing lugs. The assessment should be repeated after adding control conditions or improving the firing structure of the cutter.

[0050] The following examples illustrate the method for evaluating the firing performance of a cord cutter according to the present invention.

[0051] Step 1: Through ground firing tests of the cord cutter, determine the reliable firing range of the cord cutter and fit the relationship curve between the firing angle and the firing force.

[0052] The cutter was installed in the parachute at an angle θ (20°) and the parachute axis was offset from the direction of the pull force at an angle β (40°). The possible initial pull-out angle range during actual flight was determined to be [30°, 180°]. The pull-out angle range for ground testing, encompassing the possible initial pull-out angle range during flight, was set to [30°, 180°]. During ground testing, the drawstring cutter was fixed at a given test angle using a fixture. A pull-out tester was used to pull the firing lug at the given angle, and the pull-out force at that angle was recorded. After completing all angle tests, the reliable firing pull-out angle range for the drawstring cutter was determined to be [75°, 180°]. The relationship curve between the pull-out angle and the pull-out force was fitted using linear interpolation, see [see...]. Figure 5 .

[0053] Step 2: Establish a dynamic simulation model. Using Adams software, create a model of the cable cutter, an aircraft model, and the connecting cable between the cable cutter and the aircraft. The connecting cable is simplified to the spring force representing the simulated pull-out force applied between the firing lug of the cable cutter and the aircraft. (See...) Figure 4 .

[0054] Step 3: Set the initial conditions for the simulation. Typically, multiple uncertainties are considered, such as the initial pull-out angle α of the retractable cord cutter, the aircraft speed, the pull-out speed during the parachute pull-out process, and the speed of the retractable cord cutter. The conditions are set to cover the boundary values ​​of various angle and speed conditions.

[0055] Step 4: Conduct dynamic simulation to obtain the pull-out angle for all working conditions. When the pull-out force is greater than or equal to the pull-out force corresponding to the pull-out angle, the pull-out angle at this time is the pull-out angle under that working condition.

[0056] For example, the correspondence between the pull-out angle of a certain cutter within its operating range and the initial simulation conditions is shown in the table below. Example calculation images are shown below. Figure 6 , Figure 6 The figure shows the relationship between the pulling force and the pulling angle during the dynamic process under various working conditions. The initial state is when the pulling force is 0. During the movement, the cutter gradually rotates, the pulling angle gradually increases, and the pulling force also gradually increases.

[0057]

[0058]

[0059] Step 5: Evaluate the firing performance of the cord cutter. For the pull-out angles obtained in Step 4, if all pull-out angles are within the reliable firing range of the cord cutter, then the firing performance of the cord cutter is reliable. If any pull-out angle exceeds the reliable firing range for a given condition, then the firing performance of the cord cutter is not suitable for that operating condition.

[0060] The example cutter in step four has a pull-out angle within the range of reliable firing angles under all operating conditions, therefore the cord cutter has reliable firing performance under given conditions.

[0061] The present invention also provides a device for evaluating the firing performance of a cord cutter, comprising:

[0062] One or more processors;

[0063] Storage device for storing one or more programs.

[0064] When the one or more programs are executed by the one or more processors, the one or more processors implement the firing performance evaluation method for the cord cutter described in the first aspect.

[0065] The present invention also provides a readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method for evaluating the firing performance of a cord cutter as described in the first aspect.

[0066] The readable storage media include, but are not limited to, USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, optical disks, and other media capable of storing program code.

[0067] The present invention also provides a computer program product comprising: a computer program (also referred to as code or instructions), which, when run, executes the method for evaluating the firing performance of a cord cutter as described in the first aspect.

[0068] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, microwave, etc.) means.

[0069] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0070] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the devices, apparatuses, and modules described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0071] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0072] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for evaluating the firing performance of a cord cutter, characterized in that, include: By conducting ground firing tests on the cord cutter, the range of pull-out angles for reliable firing of the cord cutter was obtained, and the relationship curve between the pull-out angle and the pull-out force was fitted. A dynamic simulation model was established, including a model of the drawstring cutter, an aircraft model, and a connecting rope between the drawstring cutter and the aircraft. The connecting rope was simplified to the spring force of the simulated pull-out force applied between the firing lug of the drawstring cutter and the aircraft. Set the initial conditions for multi-condition simulation, carry out dynamic simulation, and obtain the pull-out angle for all conditions using the relationship curve between pull-out angle and pull-out force. Determine whether the pull-out angle for all working conditions falls within the reliable firing range of the cord cutter. If the pull-out angle for all working conditions falls within the reliable firing range of the cord cutter, then the firing performance of the cord cutter is reliable. If the pull-out angle for any working condition exceeds the reliable firing range, then the firing performance of the cord cutter does not meet the usage requirements.

2. The method for evaluating the firing performance of a cord cutter according to claim 1, characterized in that, The pull-out angle range in the ground firing test of the cord cutter encloses the possible initial pull-out angle range during flight; the possible initial pull-out angle range during flight is [α]. min ,α max ], α max =π; θ max β is the maximum installation angle of the cutter in the parachute pack. max This represents the maximum angle at which the parachute axis deviates from the direction of the tension force.

3. The method for evaluating the firing performance of a cord cutter according to claim 1, characterized in that, Based on the maximum and minimum pull-out angles recorded in the ground firing test of the cord cutter, the range of pull-out angles for reliable firing of the cord cutter is determined.

4. The method for evaluating the firing performance of a cord cutter according to claim 1, characterized in that, In the step of establishing the dynamic simulation model, the parameters of the rope cutter model include the geometric dimensions, center of mass, mass characteristics, and moment of inertia of the rope cutter. The parameters of the aircraft model include mass characteristics; The parameters of the spring force include the spring force length and the elastic coefficient. The spring force length and the elastic coefficient are the length and elastic coefficient of the firing lug pull rope and the connected rope, and are set to be under tension force and not under shortening force.

5. The method for evaluating the firing performance of a cord cutter according to claim 1, characterized in that, In the step of setting the initial conditions for multi-condition simulation, the initial conditions for multi-condition simulation include the initial pull-out angle of the retractable rope cutter, the speed of the aircraft, the pull-out speed during the parachute pull-out process, and the speed of the retractable rope cutter. The condition settings cover the boundary values ​​of various angle and speed conditions.

6. The method for evaluating the firing performance of a cord cutter according to claim 1, characterized in that, In the step of conducting dynamic simulation and obtaining the pull-out angle for all working conditions, the simulation is terminated when the pull-out force is greater than or equal to the pull-out force corresponding to the current pull-out angle. The pull-out angle at this time is the pull-out angle under the simulated working condition.

7. The method for evaluating the firing performance of a cord cutter according to claim 1, characterized in that, Also includes: If the firing performance of the cord cutter is determined to be unsatisfactory, consider improving firing reliability by controlling the initial installation angle of the cord cutter, the pull-out speed during the parachute pull-out process, or improving the performance of the firing lugs. After increasing control conditions or improving the firing structure of the cutter, the assessment should be repeated.

8. A device for evaluating the firing performance of a cord cutter, characterized in that, include: One or more processors; Storage device for storing one or more programs. When the one or more programs are executed by the one or more processors, the one or more processors implement the method for evaluating the firing performance of a cord cutter as described in any one of claims 1 to 7.

9. A readable storage medium, characterized in that, It stores a computer program that, when executed by a processor, implements the firing performance evaluation method for the cord cutter as described in any one of claims 1 to 7.

10. A computer program product, characterized in that, The computer program product includes: a computer program that, when run, executes the method for evaluating the firing performance of a cord cutter as described in any one of claims 1 to 7.

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